
// 功能: 释放文件块号为num的文件占用的空间
void release_blk(int num)
{
FILE *fp;
if((fp=fopen(image_name, "r+b")) == NULL)
{
printf("Can't open file %s\n", image_name);
exit(-1);
}
bitmap[num] = '0';
fseek(fp, num, SEEK_SET);
fputc('0', fp);
fclose(fp);
}